Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common genetic disorder in humans, with more than 160 point mutations in this gene, and over 400 million people affected. Although most research relates to G6PD deficiency and increased hemolysis (breakdown of red blood cells) and accumulation of bilirubin in adults, epidemiological studies indicate that G6PD deficiency is also a major cause of pathologic neonatal bilirubin accumulation (jaundice) and a contributor to morbidity, including neurological injury (kernicterus). The hypothesis to be tested here is that correcting the activity and stability of G6PD mutants as well as increasing the activity of the wild-type enzyme will decrease bilirubin-induced neurotoxicity in infants. In this proposal, the plan to begin developing a treatment for kernicterus using a totally novel approach, by developing activators of wild-type (Wt) and mutant G6PDs is described. The project includes four aims: AIM 1: Identify small molecule chaperones that increase the catalytic activity of Wt and common G6PD mutants using an in vitro screen of a library of small molecules. AIM 2: Determine the X-ray crystal structure of the Wt and mutant G6PD enzymes in complex with the G6PD chaperone(s). Aim 3: Evaluate the ability of the chaperone(s) to protect cultured cells expressing Wt or the mutant G6PDs from bilirubin-induced cytotoxicity and elucidate the molecular basis of their effects. AIM 4: Evaluate the ability of the small molecule chaperone(s) to reduce bilirubin-induced neurotoxicity in rodent models of newborn hyperbilirubinemia, in vivo. Two established rat models of kernicterus (Gunn rats and bilirubin-injected Wt rats) and three new mouse models [transgenic mice, mimicking three common G6PD mutations with kernicterus] will be used. Small molecules, identified in Aim 3 to protect neurons from bilirubin-induced toxicity, will be tested for their ability to prevent or reduce neurological injury (measured as loss of motor and auditory skills) due to hyperbilirubinemia in one or more of these rodent models, in vivo. The experience of Dr. Stevenson (co-PI) in basic research related to hyperbilirubinemia and in clinical care of such newborns, the expertise of Dr. Wakatsuki in crystallography, together with our expertise in drug discovery and development and in neuroscience research, and the expertise of other advisors in drug screening, medicinal chemistry, in gene editing and in assessing auditory and motor dysfunctions, place the team in a unique position to address the above goals.